There has been a growing interest in developing electronic devices using metal oxides as the semiconductor component. These devices can offer advantages such as structural flexibility (e.g., foldable or bendable), potentially much lower manufacturing costs, and the possibility of low-temperature ambient manufacturing processes on large areas. Particularly, metal oxide semiconductors such as indium gallium zinc oxide (IGZO) can exhibit high charge carrier mobility and be processed at temperatures far lower than those required for silicon. Thus, metal oxide semiconductors can be used to enable new devices such as electronic paper, rigid or flexible organic light-emitting diode (OLED) displays, ultra-high resolution displays, radio-frequency identification (RFID) technologies, and transparent displays and circuits.
One of the key benefits to using metal oxides is the potential to use both vapor-phase and solution-phase deposition techniques to deposit the semiconductor as well as other materials needed to fabricate these devices. Yet, to further realize the processing advantages of metal oxide semiconductors, all active components of the device should be mechanically flexible and, preferably, most of the components of the device should be compatible with, if not processable by, solution-phase deposition fabrication.
For example, thin-film transistors (TFTs) based upon various solution-processed or vapor-deposited metal oxide semiconductors have been developed. However, the layers in the proximity of the oxide semiconductor channel layers also are critical components in TFTs. Depending on the TFT device architecture (see FIG. 1), such critical components can include the gate dielectric layer and the etch-stop (ES) layer and/or the passivation layer.
With respect to passivation materials, a few polymeric materials have been envisioned to be used as both the ES layer and the passivation layer. However, it has remained a challenge to identify materials that show excellent thermal stability, photopatternability, and good adhesion to both inorganic (e.g, metals, metal alloys, and metal oxides) and organic materials, while also acting as a moisture barrier, planarizing the surface, and conferring chemical protection to the oxide channel layer. Particularly, conventional photoresists, while providing excellent photopatternability, fail to enable the other requirements.
Accordingly, there is a desire in the art to provide new materials that are compatible with diverse substrates, conductor, and/or semiconductor materials such that they could be employed in the whole metal oxide TFT fabrication process to meet one or more device requirements including photopatternability, low current leakage densities, high thermal stability, resistance to harsh chemicals used in patterning steps, tuned surface energies, good adhesion, good solution-processability, and/or low permeation to water.